UEFI Secure Boot requires that the operating system kernel is signed with a recognized private key, which the system’s firmware verifies using the corresponding public key.
For Red Hat Enterprise Linux Beta releases, the kernel is signed with a Red Hat Beta-specific public key, which the system fails to recognize by default.
If you plan to install a Beta release of Red Hat Enterprise Linux, on systems having UEFI Secure Boot enabled, then first disable the UEFI Secure Boot option and then begin the installation.